The Fan Resistor is a current limiting resistor/ dropping resistor. That may be why the 'low speed' circuit only needs a 30A fuse.

The high speed circuit has no series resistor, the Fan Resistor, and needs a 50A fuse.

If you short out/bypass the Fan Resistor you may exceed the 30A fuse value.
If you replace the 30A fuse with a 50A fuse you may exceed the wires current rating associated with it if it is not the correct gauge wire.

__________________
Member of the Dropped Valve Seat Club.
Replaced #4 Piston, Rings, Rod+Bearings, AERA Re-Manufactured Cylinder Head and a light Hone. Then CLEANED the hell out of everything.
60k+ miles.